This invention relates to circuitry coupled to an array of radiating elements or transducers for combining signals thereof to form beams of radiant energy and, more particularly, to such a beam forming circuit wherein the signals of the radiating elements or transducers are hard limited.
Hard clipping or limiting of signals from radiating elements or transducers arranged in an array is often utilized with beam forming circuits. A hard clipped sinusoidal signal resembles a square or trapezoidal wave signal and has the advantage of rendering the beam forming circuitry substantially insensitive to fluctuations in the amplitude of signals received at the array. The hard clipped signals preserve the zero crossings and phase data of the signals received at the array, the summation of these signals to form a beam being described vectorially as the summation of unitary vectors of differing phases.
A problem arises in that, while the clipped signal beam forming circuitry provides a well-defined main lobe in the radiation pattern of the array, the sidelobes may be excessively large with the result that the receiving circuitry coupled to the beam forming circuitry is responsive to sources of signal at the side of the array when, ideally, such receiving circuitry is to be responsive only to signals positioned in the direction of the main lobe of the radiation pattern.